Discussion on x86_64-unknown-none-hermitkernel target #197

haraldh · 2021-12-22T07:44:09Z

Followup discussion for

@haraldh I thought a little bit about your request. The main issue is that our llvm target is also defined in the spec file (see https://github.com/rust-lang/rust/blob/master/compiler/rustc_target/src/spec/x86_64_unknown_none_hermitkernel.rs#L14). This is used to define our kernel as standalone kernel (https://github.com/llvm/llvm-project/blob/e356027016c6365b3d8924f54c33e2c63d931492/llvm/include/llvm/MC/MCELFObjectWriter.h#L76-L77). In our case, we develop a library operating systems and everything is linked to one single boot image. Maybe it is currently working, but if I understand everything correctly, every part of the image should use the same OSABI. What do you think?

Originally posted by @stlankes in rust-lang/rust#89062 (comment)

haraldh · 2021-12-22T08:27:24Z

So, with x86_64-unknown-none instead of x86_64-unknown-none-hermitkernel the resulting binary is still ELFOSABI_STANDALONE

❯ readelf -h target/x86_64-unknown-hermit/debug/rusty_demo
ELF Header:
[…]
  OS/ABI:                            <unknown: ff>

❯ find target/ -name '*.a' -o -name '*.o' -print0 | xargs -0 readelf -h | grep -F 'OS/ABI' | sort -u
  OS/ABI:                            UNIX - System V
  OS/ABI:                            <unknown: ff>

Are you worried, that the linker would not want to link a ELFOSABI_NONE to a ELFOSABI_STANDALONE to produce a binary with ELFOSABI_STANDALONE ??

stlankes · 2021-12-22T08:52:30Z

Yes, I am not sure if this is correct behavior and would work also with all linkers.

We could change the OSABI of the static library with elfedit. But this isn't part of corgo-binutils. An OS-independent version of elfedit will be great.

haraldh · 2021-12-22T09:02:51Z

I don't want to introduce problems to your project... I just thought out loud on how to reduce targets with basically the same definitions.

stlankes · 2021-12-22T10:37:16Z

Yes, I completely understand. I discuss this @mkroening. Maybe we find a good solution.

In hermit-os#197 we discuss to use x86_64-unknown-none target instead of the special `kernel` target. Also the aarch64 port has to use aarch64-unknown-none-softfloat. The floating point unit should not use in the kernel space.

stlankes · 2022-01-08T12:12:40Z

@haraldh The "none"-target for aarch64 doesn't support dynamic relocation (see https://github.com/hermitcore/rusty-hermit/runs/4747837810?check_suite_focus=true). Do you think that this feature could be enabled like in x86_64-unknown-none?

haraldh · 2022-01-10T09:50:23Z

@haraldh The "none"-target for aarch64 doesn't support dynamic relocation (see https://github.com/hermitcore/rusty-hermit/runs/4747837810?check_suite_focus=true). Do you think that this feature could be enabled like in x86_64-unknown-none?

@stlankes sorry, I am not familiar with the state of the aarch64 linkers

Currently, we are thinking to use *-unknown-none targets instead to define for every platform our own one (see hermit-os/hermit-rs#197). However, the current target aarch64-unknown-none-softfloat doesn't support dynamic relocation. Our kernel uses this feature and consequently we define a new target aarch64-unknown-hermitkernel to support it.

add kernel target for RustyHermit Currently, we are thinking to use *-unknown-none targets instead to define for every platform our own one (see hermit-os/hermit-rs#197). However, the current target aarch64-unknown-none-softfloat doesn't support dynamic relocation. Our RustyHermit project uses this feature and consequently we define a new target aarch64-unknown-hermitkernel to support it. > A tier 3 target must have a designated developer or developers (the "target maintainers") on record to be CCed when issues arise regarding the target. (The mechanism to track and CC such developers may evolve over time.) I would be willing to be a target maintainer, though I would appreciate if others volunteered to help with that as well. > Targets must use naming consistent with any existing targets; for instance, a target for the same CPU or OS as an existing Rust target should use the same name for that CPU or OS. Targets should normally use the same names and naming conventions as used elsewhere in the broader ecosystem beyond Rust (such as in other toolchains), unless they have a very good reason to diverge. Changing the name of a target can be highly disruptive, especially once the target reaches a higher tier, so getting the name right is important even for a tier 3 target. Uses the same naming as the LLVM target, and the same convention as many other kernel targets (e.g. `x86_64_unknown_none_linuxkernel`). In contrast to the bare-metal target for the aarch64 architecture, the unikernel requires dynamic relocation. > Target names should not introduce undue confusion or ambiguity unless absolutely necessary to maintain ecosystem compatibility. For example, if the name of the target makes people extremely likely to form incorrect beliefs about what it targets, the name should be changed or augmented to disambiguate it. I don't believe there is any ambiguity here. It use the same convention on x86_64 architecture. > Tier 3 targets may have unusual requirements to build or use, but must not create legal issues or impose onerous legal terms for the Rust project or for Rust developers or users. I don't see any legal issues here. > The target must not introduce license incompatibilities. Anything added to the Rust repository must be under the standard Rust license (MIT OR Apache-2.0). The target must not cause the Rust tools or libraries built for any other host (even when supporting cross-compilation to the target) to depend on any new dependency less permissive than the Rust licensing policy. This applies whether the dependency is a Rust crate that would require adding new license exceptions (as specified by the tidy tool in the rust-lang/rust repository), or whether the dependency is a native library or binary. In other words, the introduction of the target must not cause a user installing or running a version of Rust or the Rust tools to be subject to any new license requirements. If the target supports building host tools (such as rustc or cargo), those host tools must not depend on proprietary (non-FOSS) libraries, other than ordinary runtime libraries supplied by the platform and commonly used by other binaries built for the target. For instance, rustc built for the target may depend on a common proprietary C runtime library or console output library, but must not depend on a proprietary code generation library or code optimization library. Rust's license permits such combinations, but the Rust project has no interest in maintaining such combinations within the scope of Rust itself, even at tier 3. Targets should not require proprietary (non-FOSS) components to link a functional binary or library. "onerous" here is an intentionally subjective term. At a minimum, "onerous" legal/licensing terms include but are not limited to: non-disclosure requirements, non-compete requirements, contributor license agreements (CLAs) or equivalent, "non-commercial"/"research-only"/etc terms, requirements conditional on the employer or employment of any particular Rust developers, revocable terms, any requirements that create liability for the Rust project or its developers or users, or any requirements that adversely affect the livelihood or prospects of the Rust project or its developers or users. I see no issues with any of the above. > Neither this policy nor any decisions made regarding targets shall create any binding agreement or estoppel by any party. If any member of an approving Rust team serves as one of the maintainers of a target, or has any legal or employment requirement (explicit or implicit) that might affect their decisions regarding a target, they must recuse themselves from any approval decisions regarding the target's tier status, though they may otherwise participate in discussions. This requirement does not prevent part or all of this policy from being cited in an explicit contract or work agreement (e.g. to implement or maintain support for a target). This requirement exists to ensure that a developer or team responsible for reviewing and approving a target does not face any legal threats or obligations that would prevent them from freely exercising their judgment in such approval, even if such judgment involves subjective matters or goes beyond the letter of these requirements. Only relevant to those making approval decisions. > Tier 3 targets should attempt to implement as much of the standard libraries as possible and appropriate (core for most targets, alloc for targets that can support dynamic memory allocation, std for targets with an operating system or equivalent layer of system-provided functionality), but may leave some code unimplemented (either unavailable or stubbed out as appropriate), whether because the target makes it impossible to implement or challenging to implement. The authors of pull requests are not obligated to avoid calling any portions of the standard library on the basis of a tier 3 target not implementing those portions. `core` and `alloc` can be used. For `std` exists already the target `aarch64_unknown_hermit`, which enables FPU support. > The target must provide documentation for the Rust community explaining how to build for the target, using cross-compilation if possible. If the target supports running tests (even if they do not pass), the documentation must explain how to run tests for the target, using emulation if possible or dedicated hardware if necessary. Use `--target=aarch64_unknown_hermitkernel` option to cross compile. The target does currently not support running tests. > Tier 3 targets must not impose burden on the authors of pull requests, or other developers in the community, to maintain the target. In particular, do not post comments (automated or manual) on a PR that derail or suggest a block on the PR based on a tier 3 target. Do not send automated messages or notifications (via any medium, including via `@)` to a PR author or others involved with a PR regarding a tier 3 target, unless they have opted into such messages. Backlinks such as those generated by the issue/PR tracker when linking to an issue or PR are not considered a violation of this policy, within reason. However, such messages (even on a separate repository) must not generate notifications to anyone involved with a PR who has not requested such notifications. I don't foresee this being a problem. > Patches adding or updating tier 3 targets must not break any existing tier 2 or tier 1 target, and must not knowingly break another tier 3 target without approval of either the compiler team or the maintainers of the other tier 3 target. In particular, this may come up when working on closely related targets, such as variations of the same architecture with different features. Avoid introducing unconditional uses of features that another variation of the target may not have; use conditional compilation or runtime detection, as appropriate, to let each target run code supported by that target. No other targets should be affected by the pull request.

bstrie · 2022-03-23T14:06:21Z

@stlankes @mkroening We're about to proceed with proposing that x86_64-unknown-none be made a Tier 2 platform. One of the minor questions from the original Tier 3 addition was whether or not this target would suffice to replace the x86_64-unknown-none-hermitkernel target, to avoid a profusion of similar targets. Do you think that x86_64-unknown-none would suffice for your needs, allowing Rust to remove the x86_64-unknown-none-hermitkernel target?

mkroening · 2022-03-23T18:18:09Z

Since we want to use our own llvm-target for now, we can't switch to x86_64-unknown-none. We should be able to maintain our target specification in this repository instead of the Rust repository though. I opened hermit-os/kernel#395 for that.

I can create PRs removing the hermitkernel targets from the Rust repository once hermit-os/kernel#395 is merged.

bstrie · 2022-03-23T18:26:50Z

Out of curiosity, is the desire not to use x86_64-unknown-none due to some deficiency in the target? If so, then it might make sense for us to try to address it before moving it to Tier 2.

mkroening · 2022-03-23T20:27:08Z

The only relevant difference between the targets is "llvm-target": "x86_64-unknown-hermit" as opposed to "llvm-target": "x86_64-unknown-none-elf". The other differences can be removed on our side in the future. Functionally, x86_64-unknown-none works fine for us.

The effect of our llvm-target is some magic number shenanigans in the resulting library archive. This could be achieved as well via manual post-processing in the future (using xtasks introduced in hermit-os/kernel#378), as moving to a higher tier target might be worth the effort.

This is not a deficiency in x86_64-unknown-none, as this is hermit-specific, and should not require any change in x86_64-unknown-none.

bstrie · 2022-03-23T20:35:54Z

Great, thanks for the info!

mkroening · 2022-03-25T10:53:07Z

I opened rust-lang/rust#95299.

…iplett Remove hermitkernel targets RustyHermit now maintains custom json targets, which are distributed with the kernel: hermit-os/kernel#395 See hermit-os/hermit-rs#197 (comment) CC: `@stlankes,` `@bstrie`

…iplett Remove hermitkernel targets RustyHermit now maintains custom json targets, which are distributed with the kernel: hermit-os/kernel#395 See hermit-os/hermit-rs#197 (comment) CC: ``@stlankes,`` ``@bstrie``

…lett Remove hermitkernel targets RustyHermit now maintains custom json targets, which are distributed with the kernel: hermit-os/kernel#395 See hermit-os/hermit-rs#197 (comment) CC: `@stlankes,` `@bstrie`

414: Targets: Use none-elf instead of hermit llvm-target r=stlankes a=mkroening As discussed in hermit-os/hermit-rs#197 (comment), this way the kernel's `libhermit.a` has `OS/ABI: UNIX - System V` and the resulting application has `OS/ABI: <unknown: ff>`. This works for the Rust-toolchain as well as the C-toolchain. 422: Condvar: Mark sys functions as extern "C" r=stlankes a=mkroening They are declared in hermit-abi as extern "C" already. So the current definition without extern "C" is wrong. 424: Clippy: Enable and fix transmute_ptr_to_ptr r=stlankes a=mkroening Co-authored-by: Martin Kröning <mkroening@posteo.net> Co-authored-by: Martin Kröning <m.kroening@hotmail.de>

414: Targets: Use none-elf instead of hermit llvm-target r=stlankes a=mkroening As discussed in hermit-os/hermit-rs#197 (comment), this way the kernel's `libhermit.a` has `OS/ABI: UNIX - System V` and the resulting application has `OS/ABI: <unknown: ff>`. This works for the Rust-toolchain as well as the C-toolchain. Co-authored-by: Martin Kröning <mkroening@posteo.net>

414: Targets: Use none-elf instead of hermit llvm-target r=stlankes a=mkroening As discussed in hermit-os/hermit-rs#197 (comment), this way the kernel's `libhermit.a` has `OS/ABI: UNIX - System V` and the resulting application has `OS/ABI: <unknown: ff>`. This works for the Rust-toolchain as well as the C-toolchain. 422: Condvar: Mark sys functions as extern "C" r=stlankes a=mkroening They are declared in hermit-abi as extern "C" already. So the current definition without extern "C" is wrong. Co-authored-by: Martin Kröning <mkroening@posteo.net> Co-authored-by: Martin Kröning <m.kroening@hotmail.de>

haraldh mentioned this issue Dec 22, 2021

Add new tier 3 target: x86_64-unknown-none rust-lang/rust#89062

Merged

stlankes mentioned this issue Jan 8, 2022

removing kernel targets #202

Closed

stlankes mentioned this issue Jan 8, 2022

add kernel target for RustyHermit rust-lang/rust#92670

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mkroening self-assigned this Mar 23, 2022

mkroening mentioned this issue Mar 23, 2022

Use custom targets for kernel hermit-os/kernel#395

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bors bot closed this as completed in hermit-os/kernel@6e28975 Mar 24, 2022

bors bot closed this as completed in hermit-os/kernel#395 Mar 24, 2022

mkroening mentioned this issue Mar 25, 2022

Remove hermitkernel targets rust-lang/rust#95299

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This was referenced Mar 27, 2022

Migrate to x86_64-unknown-none hermit-os/kernel#412

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Targets: Use none-elf instead of hermit llvm-target hermit-os/kernel#414

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Discussion on x86_64-unknown-none-hermitkernel target #197

Discussion on x86_64-unknown-none-hermitkernel target #197

haraldh commented Dec 22, 2021

haraldh commented Dec 22, 2021

stlankes commented Dec 22, 2021

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Discussion on x86_64-unknown-none-hermitkernel target #197

Discussion on x86_64-unknown-none-hermitkernel target #197

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haraldh commented Dec 22, 2021

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